The largest living organism on Earth is the Armillaria ostoyae fungus, also known as the honey fungus. It is a single organism that covers an area of over 2,300 acres in the Blue Mountains of Oregon, USA. The fungus is estimated to be between 2,400 and 8,650 years old. It is thought that the fungus started as a single spore and has since grown to its current size through asexual reproduction. The fungus is made up of a network of mycelia, which are thread-like hyphae. The mycelia can grow underground for long distances and can even penetrate through solid rock. The fungus produces mushrooms, which are the fruiting bodies of the organism. The mushrooms can grow up to 12 inches in diameter and can be found in large clusters.